Sen. Jesse A. Helms (R-N.C.) has agreed to unblock several State Department nominations after getting a personal assurance from President Reagan that the nominees were okay by him.

Helms, explaining why he had put the pinch on the nominations, told Senate Foreign Relations Committee Chairman Charles. H. Percy (R-Ill.) in a long letter last weekend that he was simply trying to make sure that policy makers "reflect, to the fullest extend possible, the president's views."

In a telephone conversation Wednesday, Helms said, Reagan "expressed gratitude that I was monitoring these nominations so carefully."

The informal holds, which essentially keep a nomination off the Senate floor out of courtesy, will stay on, however, for two nominees: Chester Crocker as assistant secretary of state for African affairs, who Helms said "responded to my written questions with mush," and Myer Rashish as undersecretary of state for economic affairs. Helms wasn't sure Rashish had responded to his written questions.

Both of these nominations were voted out of the Foreign Relations Committee this week, 14 to 0, despite Helms' objections.

Even with the president's assurances, the released nominees can't count on Helms' vote. "I may vote against one or more of them," he said yesterday.